The traditional distribution of social classes historically was something like 90%+ working+lower classes (farmers/craftsmen/factory workers/service jobs/soldiers/etc) 9% middle class (merchants, doctors, lawyers, officers, scholars, managers) and 1% or so of upper class (landlords, aristocracy and capitalists; CEOs and politicians). Middle class grew much larger in mid-20th century USA, exceeding 50% but perhaps that's just a temporary situation that's now reversing as the inequity has been significantly increasing in the last 50 years or so and it looks like in the future middle class might be a minority forever - IIRC current stats would be something like 1-2% of upper class, 45% middle class, and the remaining 53% or so working+lower classes.
If you look at social class stratification, the general assumption is that if you have to work a job for your income, you're not upper class, you're serving in the employment of the upper class. If you have a high paying job, that's defined as "upper middle" social class at least until you have accumulated wealth to transition to a capitalist/owner/investor role (as some popular musicians and athletes do); being in the top 4% of earners is quite reasonable for traditional upper middle class roles e.g. independent lawyers and doctors, which also tend to earn 200k+/year in USA.
